1. Field of the Invention
The invention relates to a radar high frequency module comprising a printed circuit board carrying microwave components including a patch antenna, a shielding cover having a flat top wall and downwardly extending side walls and being positioned on the printed circuit board to cover the microwave components, and a dielectric rod antenna extending through and being held in a hole in the top wall of the shielding cover and being transmissively coupled to the patch antenna.
2. Description of the Related Art
A dielectric rod antenna may be used as a system antenna or as a pre-focusing member for illuminating a dielectric lens placed in front of the dielectric rod antenna to form narrow beams. Alternatively, the radiation may be fed into other beam forming type devices, such as a horn, a waveguide extended horn or a reflector antenna.
U.S. Pat. No. 6,366,245 B1 discloses a radar high frequency module of the above-mentioned type wherein the dielectric rod antenna is held in a bushing in the shielding cover. Actually, and as disclosed in the corresponding DE 198 59 002 A1, the figures show a hole rather than a bushing, in which hole or bushing the dielectric rod antenna may be inserted in an injection molding process. The printed circuit board is disposed on a base plate to which the shielding cover is fixed at three fixing points by screws, bonding or the like.
U.S. Pat. No. 5,757,323 shows a similar radar high frequency module where the dielectric rod antenna is adjustably mounted in a thread in the shielding cover. The dielectric rod antenna comprises a tubular tapered section adjacent the patch antenna.
The performance of the radar module is strongly dependant on the alignment of the dielectric rod antenna to the patch antenna. Thus, especially as the radar frequency becomes higher, it is necessary to align the rod to the patch with greater precision and to maintain this placement in a robust fashion which can be easily handled during assembly of the complete radar product. For example, at 77 GHz typically the rod must be aligned to the patch with a precision of 0.2 mm.